The present invention relates to compositions suitable for use as particulates in subterranean operations, such as proppant or gravel. More particularly, the present invention relates to particulate composites comprising at least one resin and at least one nanoparticle material.
Servicing fluids comprising particulates are used in a variety of operations and treatments performed in oil and gas wells. Such operations and treatments include, but are not limited to, production stimulation operations such as fracturing, well completion operations such as gravel packing, and combined operations such as frac-packing.
An example of a production stimulation operation using a servicing fluid having particles suspended therein is hydraulic fracturing, wherein a servicing fluid known as a fracturing fluid is pumped through a well bore into a portion of a subterranean formation at a rate and pressure such that fractures are formed and/or extended into the subterranean zone. The fracture or fractures may range from horizontal to vertical, with the latter usually predominating, and with the tendency toward vertical fracture orientation with the depth of the formation being fractured. The fracturing fluid is generally a gel, emulsion, or foam that may comprise a particulate material often referred to as proppant. Proppant may be deposited in a fracture and function, inter alia, to hold the fracture open while maintaining conductive channels through which produced fluids can flow upon completion of the fracturing treatment and release of the attendant hydraulic pressure.
An example of a well completion operation using a servicing fluid containing particulates is gravel packing. Gravel packing treatments are used, inter alia, to reduce the migration of unconsolidated formation particulates into the well bore. In gravel packing operations, particles referred to in the art as gravel are carried to a well bore in a portion of a subterranean formation by a hydrocarbon or water-based carrier fluid. That is, the particulates are suspended in a carrier fluid, which may be viscosified, and the carrier fluid is pumped into a well bore in which the gravel pack is to be placed. As the particulates are placed in the zone, the carrier fluid leaks off into the subterranean zone and/or may be returned to the surface after passing through a screen positioned adjacent to the productive interval. The resultant gravel pack acts as a filter to separate formation solids from produced fluids while permitting the produced fluids to flow into and through the well bore. Traditional gravel pack operations involve placing a gravel pack screen in the well bore and packing the surrounding annulus between the screen and the well bore with gravel sized to prevent the passage of formation particulates through the pack with produced fluids. The gravel pack screen is generally a filter assembly used to support and retain the gravel placed during the gravel pack operation. A wide range of sizes and screen configurations are available to suit the characteristics of a well bore, the production fluid, and any particulates in the subterranean formation. Gravel packs may be used to stabilize a portion of a formation while causing minimal impairment to well productivity. The gravel, inter alia, acts to prevent the particulates from occluding the screen or migrating with the produced fluids, and the screen, inter alia, acts to prevent the gravel from entering the well bore.
In some situations the processes of hydraulic fracturing and gravel packing are combined into a single treatment to provide a stimulated production and an annular gravel pack to prevent formation sand production. Such treatments are often referred to as “frac pack” operations. These treatments are often completed with a gravel pack screen assembly in place with the hydraulic fracturing treatment being pumped through the annular space between the casing/open hole and screen. In this situation the hydraulic fracturing treatment is typically designed to screen out at the fracture tip, creating a packed fracture and an annular gravel pack between the screen and casing/open hole. This allows both the hydraulic fracturing treatment and gravel pack to be placed in a single operation. In other cases the fracturing treatment may be performed prior to installing the screen and placing a gravel pack.
Servicing fluids such as fracturing fluids, gravel packing carrier fluids, and frac pack fluids, generally must be highly viscous to be able to suspend particulates. To achieve a high viscosity, viscosifiers often are added to such fluids. Such viscosifiers are expensive. Moreover, as a fracture or a gravel pack is created a portion of the liquid contained in the fluid may leak off into the formation and create a filter cake comprising deposited viscosifier on the walls of the fracture, well bore, and/or the formation.
Filter cakes are sometimes desirable to aid in preventing drilling and other servicing fluids from being lost in the formation and to prevent solids from entering the porosities of the producing formation. However, just as a filter cake may block the loss of fluids into the formation, the same filter cake may block the production of fluids from the formation. Thus, the presence of a filter cake on a producing zone is generally undesirable when a subterranean formation is returned to production. Moreover, residue of viscosifiers used in subterranean applications often remains on the particulates transported in the viscosified fluid and may reduce the conductivity of packs made from such particulates. Chemicals, referred to in the industry as “breakers,” are often incorporated into the servicing fluid to minimize this problem.
Resin materials generally exhibit relatively low specific gravities and are attractive for preparing particulates that can be used in subterranean operations. Their low specific gravity allows them to be transported to the production zone with servicing fluids having reduced viscosity as compared to traditional servicing fluids that are designed to carry traditionally high specific gravity (greater than about 2.4) particulates. However, previously developed resin particulates have not exhibited sufficient mechanical properties (such as crush strength and stiffness) to enable them to be suitable for use in subterranean operations.
Recently, the automotive, medical, and aviation arts have begun to explore the use of composite materials encompassing nanoparticles. Virtually all types and classes of nanocomposites tested exhibit new and improved properties over their microparticle and larger counterparts. The mechanical properties that are often benefited include stiffness, strength, heat resistance, moisture absorption, and permeability.